Image enhancement system and method for night goggles

ABSTRACT

A dichroic type narrow-band-pass filter is used as a beamsplitter inside a night vision goggle eyepiece. The filter is combined with appropriately aligned polarizers and liquid crystal type shutter rotators movable between a “P” orientation and an “S” orientation to transmit center band and side band wavelengths of the normal view or night scene for recording, transmitting or enhancing. In the enhanced low light level mode, the intensified visible image presented to the user comprises a 40 degree circular image with a 30 degree by 22.5 degree rectangular display insert.

RELATED APPLICATION

This application claims priority on a U.S. provisional patentapplication, U.S. Ser. No. 60/258,648, titled MODULAR PANORAMIC NIGHTVISION GOGGLES, filed Dec. 29, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an image enhancement system and method fornight vision goggles that utilizes a spectral beamsplitter to enhancethe low-light level sensitivity and resolution of the system, to enablethe night missions to be recorded for later analyses, to transmit thevideo images of the night scene to a remote location in real time, andto insert or overlay the intensified image with images from othersensors and/or data.

2. Discussion of Related Art

Existing night vision systems have many applications in every day life.Perhaps the most well known use for night vision systems is by themilitary when performing nighttime maneuvers. The night vision systemspermit vision under very low light conditions by converting incominginfrared and/or visible light from a viewed scene to an intensifiedvisible light image. During nighttime maneuvers, military personnel areoften performing other tasks, such as piloting an aircraft or driving avehicle, which require the freedom of their hands while they arescanning the territory. Accordingly, night vision systems have beendeveloped to be worn upon the head of a user, such as goggles beingsecured directly on the head or by being mounted to a helmet or a visor.

Placing a night vision system on the head of a user places significantconstraints upon the optical design of the system. For example, gogglesworn upon the head of a user must be both compact and light in weightbecause excessive weight or front-to-back length of the goggles cancause the goggles to exert large moments on the user's head causingsevere instability problems and preventing their effective use inapplications in which the user's head may be subjected to highgravitational or centrifugal loads. Furthermore, in a wide field of viewoptical system, the focal length of the eyepiece optics must beshortened correlatively that of the wide angle objective for unitymagnification; and, in night vision goggles, this results ininsufficient eye relief between the eyepiece optics and the eye, whichnot only causes discomfort to the user, but also interferes with theability to position a helmet visor, eyeglasses and other structuresbetween the goggles and the eyes of the user. In order to compensate forinadequate eye relief, prior night vision goggles have generally beenlimited to providing a field of view of no more than about 40 degrees.

Night visions goggles have been used in military aviation for severalyears with fields of views ranging from 30 degrees (Early Cat's Eyesnight vision goggles from GEC-Marconi Avionics) to 45 degrees (NITE-OPand NITE-Bird night vision goggles, also from GEC-Marconi Avionics). Thevast majority of night vision goggles used in military aviation have a40-degree field of circular view (AN/AVS-6 and AN/AVS-9). A majorlimitation of such prior art devices is that increased field of viewcould only be obtained at the expense of resolution since each ocularuses only a single image intensifier tube and each image intensifiertube has a fixed number of pixels. Therefore, if the fixed numbers ofpixels is spread over a larger field of view, then the angular subtenseper pixel increases, which translates into reduced resolution.Understandably increased field of view is a major enhancement desired bymilitary aviators, closely followed by resolution. In conventionalgoggles, both eyes also typically see the same field of view, i.e.,there is a 100-percent overlap of the image viewed by both eyes of theobserver. Such a limited field of view greatly restricts theeffectiveness of the night vision apparatus.

U.S. Pat. No. 5,229,598 addresses the above-mentioned problems anddiscloses a compact, lightweight, night vision system capable ofproviding an enlarged field of view of up to 60 degrees with improvedvisual acuity and sufficient eye relief.

In addition to night vision systems, other imaging systems, such ashand-held binoculars, typically provide a rather limited field of view;and it would be desirable to provide such systems with increased fieldsof view as well. Individually sealed and self-contained constituentmodular elements capable of providing some of the above-desiredfeatures, respectively, would enable such an imaging system to be builtincrementally as desired.

SUMMARY OF THE INVENTION

The present invention regards a modular, binocular-like vision systemfor enabling an observer to view an object. The system includes an inputend that receives light from the object and an optical transfer systemthat receives the light received from the input end and transfers thereceived light to an image intensifier which intensifies the receivedlight, wherein the intensified received light is transferred to andtransmitted out of an output end of the system, wherein the lighttransmitted out of the output end forms a field of view of the objectthat is greater than a 60-degree horizontal field of view.

Another aspect of the present invention regards a binocular-like visionsystem for enabling an observer to view an object. The system includes afirst optical component having a first input end that receives lightfrom the object and a first output end that receives light from thefirst input end, wherein the first output end defines a first opticalaxis along which light received from the first input end is transmitted.A second optical component having a second input end that receives lightfrom the object and a second output end that receives light from thesecond input end, wherein the second output end defines a second opticalaxis along which light received from the second input end istransmitted. A third optical component comprising a third input end thatreceives light from the object and a third output end that receiveslight from the third input end, wherein the third output end defines athird optical axis along which light received from the third input endis transmitted, wherein light transmitted along the first, second andthird optical axes forms a field of view comprising a first portionhaving a monocular effect on the observer and a second portion having abinocular effect on the observer.

Another aspect of the present invention regards a binocular-like visionsystem for enabling an observer to view an object. The system includes afirst optical component having a first input end that receives lightfrom the object and a first output end that receives light from thefirst input end, wherein the first output end defines a first opticalaxis along which light received from the first input end is transmitted.A second optical component having a second input end that receives lightfrom the object and a second output end that receives light from thesecond input end, wherein the second output end defines a second opticalaxis along which light received from the second input end istransmitted. A third optical component having a third input end thatreceives light from the object and a third output end that receiveslight from the third input end, wherein the third output end defines athird optical axis along which light received from the third input endis transmitted, wherein light transmitted along the first, second andthird optical axes is simultaneously transmitted from the binocular-likevision system to the observer.

In a further preferred embodiment of this invention, a panoramic nightvision goggle (PNVG) is provided that, like the previous embodiment,features a partial overlap 100-degree horizontal by 40-degree verticalintensified field of view. Again, the central 30-degree horizontal by40-degree vertical field of view is completely binocular, while theright 35 degrees is still seen with the right eye only and the left 35degrees is viewed by the left eye only. Additionally, a thin line ofdemarcation separates the binocular scenes from the outside monocularscenes. This embodiment also utilizes the newly developed 16-mm imageintensifier tube, dual fixed eyepieces, which are tilted and fusedtogether, and four objective lenses, the inner two being adjustable andthe outer two being fixed. The inner optical channels are not folded andare designed with fast F/1.05 objective lenses. The outboard channelsuse the folded inner channel optics design with F/1.17 objective lenses.The effective focal length of the eyepiece is 24.0 mm, while thephysical eye clearance has been increased to 27 mm. All of themechanical adjustments currently used on the AN/AVS-6 and AN/AVS-9 arethe same (i.e., tilt, independent inter-pupilary distance adjustment,up/down, and fore/aft). This further embodiment may also be equippedwith a heads-up display (HUD) if desired.

In yet another embodiment, the PNVG goggle is designed so that theindividual optical channels are modular and thus detachable from eachother. Each optical channel is a separately sealed and self-containedmodule. Removal of any single module from the PNVG assembly will notbreak any pressure seals or degrade the optical performance of theremoved module or the remaining modules. Electrical power andinformation (i.e., data signals and the like) required by a module isprovided through electrical connectors provided between the modules. Themodules include means of attachment that ensures proper positioning andalignment of the adjacently mating modules. In a preferred embodiment,an integral electrical connector is contained within each module thatenables the electrical connection between adjacent modules to be madesimultaneously with the mechanical attachment of the module.

In addition to the modularity of the four primary optical channels ofthe PNVG assembly, the display (i.e., HUD) and camera are modular aswell. Similar to the individual optical modules, each of thesecomponents are separately sealed and self-contained modules as well.Removal of the camera or display will not break any pressure seals ordegrade the performance of the removed module or the remaining modules.Again, electrical power and information (i.e., data signals and he like)required by the camera or display is provided by electrical connectorsmeans provided on each module.

Thus, in one preferred embodiment, this invention presents an apparatusthat significantly increases the field of view of night vision gogglesutilizing four modular optical components to produce a panoramic fieldof vision. This invention also presents the advantage of providing anenlarged field of view with improved visual acuity and sufficient eyerelief for a compact, lightweight, modular, binocular-like visionsystem.

In a further preferred embodiment, a panoramic night vision goggle isprovided having enhanced low-light level sensitivity and resolution, aswell as the ability to record the night sessions for later analyses, totransmit the video data of the night scene to a remote location in realtime, and to insert or overlay the intensified image of the night scenewith images from other sensors and/or data.

To achieve these objectives, a dichroic type narrow-band-pass filter isused as a beamsplitter positioned inside the eyepiece of the nightvision goggle. This filter is combined with appropriately alignedpolarizers and rotators to direct the intensified images of the nightscene for recording, transmitting or further video processing. Aminiature video camera captures the intensified scene, which in normallight levels allows the video to be recorded or transmitted to remotelocations. In low light, however, the weak video signal of the videocamera is electronically enhanced and amplified such that a much clearervisual image of the night scene is displayed through the eyepiece.

In order to maximize the light signal level to the video camera, thenarrow-band-pass filter is designed to reflect completely those sidebands of the image intensifier that should not be transmitted by theeyepiece to the user's eye.

To provide for the insertion of different sensor images and to avoidsuperimposing the image from the display on the image from the imageintensifier, a liquid crystal (LC) type shutter is positioned close tothe image plane of the image intensifier. The shutter may be a singlerectangular shape pixel or a multi-pixel type at selected areasspecified by the user. This shutter is, at the same time, a rotator ofpolarization, used to switch the system to a different mode as needed,such as between a “direct view” mode at normal light levels and anenhanced low-light level (ELLL) mode during night or low-light levelmissions.

Further advantages and specific details of the invention will be setforth hereinafter in conjunction with the following detailed descriptionof presently preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a binocular-like vision system according to thepresent invention;

FIG. 2 is a rear view of the binocular-like vision system of FIG. 1;

FIG. 3 schematically shows the field of view generated by thebinocular-like vision system of FIG. 1;

FIG. 4 is a top view of a second embodiment of a binocular-like visionsystem according to the present invention;

FIG. 5 is a rear view of the binocular-like vision system of FIG. 4;

FIG. 6 schematically shows the field of view generated by thebinocular-like vision system of FIG. 4;

FIG. 7 is a top view of a third embodiment of a binocular-like visionsystem according to the present invention;

FIG. 8 is a rear view of the binocular-like vision system of FIG. 7;

FIG. 9 schematically shows the field of view generated by thebinocular-like vision system of FIG. 7;

FIG. 10 is a front view of a fourth embodiment of a binocular-likevision system according to the present invention;

FIG. 11 is a bottom view of the binocular-like vision system of FIG. 10;

FIG. 12 schematically shows the field of view generated by thebinocular-like vision system of FIG. 10;

FIG. 13 schematically illustrates a head up display (HUD) superimposedon the field of view of FIG. 12;

FIG. 14 is a front view of the binocular-like vision system of FIG. 10with a mounting structure for attachment to a helmet;

FIG. 15 is a bottom view of the binocular-like vision system of FIG. 14;

FIG. 16 shows a top view of a prior art binocular-like vision system andthe field of view generated by the system;

FIG. 17 shows a top view of a fifth embodiment of a binocular-likevision system according to the present invention and the filed of viewgenerated by the system;

FIG. 18 is a front view of a sixth embodiment of a binocular-like visionsystem according to the present invention;

FIG. 19 is a top view of the binocular-like vision system of FIG. 18;

FIG. 20 is a rear view of the binocular-like vision system of FIG. 18;

FIG. 21 is a partially exposed top view of the binocular-like visionsystem of FIG. 18;

FIG. 22 shows a side view of the binocular-like vision system of FIG.18;

FIG. 23 shows an exposed side view of the binocular-like vision systemof FIG. 22;

FIG. 24 is a top view of a binocular-like vision system according to aseventh embodiment of the present invention;

FIG. 25 is a rear view of the binocular-like vision system of FIG. 24;

FIG. 26 schematically shows the field of view generated by thebinocular-like vision system of FIG. 24;

FIG. 27 is a top view of the binocular-like vision system of FIG. 24including a head up display (HUD);

FIG. 28 is a rear view of the binocular-like vision system of FIG. 27;

FIG. 29 schematically shows the field of view generated by thebinocular-like vision system of FIG. 27 including a HUD unit;

FIG. 30 is a front perspective view of a modular embodiment of thisinvention mounted to a helmet visor;

FIG. 31 is a front perspective view of the modular embodiment of thisinvention in isolation;

FIG. 32 is a front perspective view of the modular embodiment of thisinvention showing the outer optical channels detached;

FIGS. 33 and 34 present top and rear plan views, respectively, of themodular embodiment of this invention showing the outer optical modulesdetached;

FIGS. 35 and 26 are top and rear plan views, respectively, of thismodular invention showing the outer optical channels attached;

FIG. 37 is a perspective view of an outer optical module of thisinvention shown in isolation;

FIG. 38 schematically shows the field of view generated by the modularembodiment of this invention;

FIG. 39 shows in perspective the inner left and inner right opticalmodules; and

FIG. 40 is an exploded view showing the separate module elements formingthe modular panoramic night vision assembly of this invention.

FIG. 41 is a schematic illustration showing operation of the beamsplitter, polarizers and rotators in the low light level mode.

FIG. 42 graphically depicts the wavelengths of light energy transmittedthrough and reflected by the beam splitter of the invention.

FIG. 43 is a schematic illustration showing operation of the beamsplitter, polarizers and rotators in the enhanced low light level (ELLL)mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Several binocular-type-viewing systems according to the presentinvention are schematically shown in FIGS. 1–23, wherein like elementsare identified by like numerals. A wide-angle lens group that provide adesired field of view of, for example, 40 degrees and can be ofconventional design, such as disclosed in U.S. Pat. No. 5,416,315, theentire contents of which are incorporated herein by reference. Theobjective optical system 66 includes approximately 2 to 7 opticalelements, such as plastic or glass lenses L, which have an effectivefocal length of approximately 21-mm, F/1.2. The lenses L of theobjective optical system are preferably spherical or aspherical indesign.

The objective optical system 66 is designed to receive light from anobject being viewed at the input end 72 and to transfer an image of theobject to the input end or photocathode side 74 of the image intensifiertube 68.

The image intensifier tube 68 makes it possible for the observer to viewan object in dark conditions by receiving the visible and/or infraredlight image of the object transferred to the input end 74 thereof Theimage intensifier tube 68 converts the received image to an intensifiedvisible output image in a predetermined narrow band of wavelengths atthe output end 78 of the image intensifier tube 68. The imageintensifier tube 68 is well known in the art. For example, the imageintensifier tube 68 may include a GaAs photocathode at the input end 74and the binocular-like vision systems 50 of FIGS. 1–23 generally have aninput end (72, 90) that receives light from an object and an opticaltransfer system (62, 64, 86, 88) that receives the light received fromthe input end and transfers the received light to an output end (80, 92)of the system, wherein light transmitted out of the output end forms afield of view of the object that is greater than a 60 degree horizontalfield of vision.

FIGS. 1–3 show one embodiment of a binocular-like vision system 50according to the present invention that operates in the above-describedmanner. The vision system 50 is contained in a housing assembly 52 whichhas a pair of housings 54 and 56 connected to one another by a bridge 57and are arranged for respectively covering the right eye 58 and the lefteye 60 of an observer. A pair of eyelets 61 are provided in the housings54 and 56 to receive a strap or the like so that the user canconveniently carry the vision system 50 around his neck when not in use.

Each of housings 54 and 56 contain identical optical systems which aremirror images of each other about a plane 63 (denoted by dashed lines)that bisects the housing assembly 52 as shown in FIG. 1. Accordingly,the discussion to follow regarding the housing 54 is equally applicableto the housing 56.

As shown in FIG. 1, the housing 54 includes two separate opticalcomponents 62 and 64. The inner optical component 62 has the identicaloptical structure as the outer optical component 64. Accordingly, thediscussion to follow regarding the structure of the inner opticalcomponent 62 is equally applicable to the outer optical component 64.The inner optical component 62 includes three main opticalstructures—(1) an objective optical system 66, (2) an image intensifiertube 68 and (3) an eyepiece optical system 70. The objective opticalsystem 66 defines an input end 72 that receives light from an object.The objective optical system 66 includes output light from the imageintensifier tube 68 is emitted by a green phosphor producing a visibleband of light which is known as “P-20” light, although it will beappreciated that other image intensifier constructions could also beused.

The image intensifier tube 68 also includes a fiber optic bundle(schematically shown at 75) for transmitting bits of image data from thephotocathode input end 74 to the phosphor output end 78 thereof. Thefiber optic bundle 75 is preferably twisted in a manner well known inthe art to provide an image rotation of 180 degrees so that an uprightimage of the object will be presented to the eye of the user.

The intensified visible output image generated by the image intensifiertube 68 is transferred to an output end 80 of the inner opticalcomponent 62 via the eyepiece optical system 70. The light transmittedthrough the output end 80 is transmitted along the optical axis 84 thatis aligned with the optical axis of the right eye 58. The eyepieceoptical system 70 can be of conventional design, such as disclosed inU.S. Pat. No. 5,416,315, the entire contents of which are incorporatedherein by reference. The eyepiece optical system 70 includesapproximately 2 to 7 optical elements, such as plastic or glass lensesL, which have an effective focal length of approximately, 21 mm, F/1.2.The lenses L of the objective optical system are preferably spherical oraspherical in design.

In order to enlarge the field of view, an outer optical component 64 isprovided which also directs light from the object to the observer. Asexplained previously, the outer optical component 64 has the sameoptical structure as the inner optical structure 62 previouslydescribed. Like the inner optical component 62, the outer opticalcomponent 64 includes an objective optical system 66, an imageintensifier tube 68 and an eyepiece optical system 70 which operate inthe same manner as their counterparts in the inner optical component 62.Accordingly, the objective optical system 66 and the eyepiece opticalsystem 70 of the outer optical component 64 each have an effective focallength of approximately 21-mm like their counterparts in the inneroptical component 62.

The above-described outer optical component 64 operates in a mannersimilar to that of the inner optical component 62. The input end 72 ofthe outer optical component 64 receives light from an object. Thereceived light is then transferred via the objective optical system 66to the image intensifier which in turn generates an intensified imagethat is received by the eyepiece optical system 70. The eyepiece opticalsystem 70 then sends the image to an output end 80 of the outer opticalcomponent 64. The light transmitted through the output end 80 travelsalong an optical axis 82 that is offset from the optical axis 84 by anangle ranging from approximately 30° to 35° and which is preferably 30degrees.

As stated previously, the inner optical component 86 for the left eye 60has the same structure and operates in the same manner as the inneroptical component 62. Similarly, the outer optical component 88 for theleft eye 60 has the same structure and operates in the same manner asthe outer optical component 64. In other words, the inner and outeroptical components 86 and 88 each receive light from an object at theinput ends 90 and transfer their images of the object to respectiveoutput ends 92. As shown in FIG. 1, the image from the inner opticalcomponent 86 intensifier tube 68 which is projected along an opticalaxis 94 that is aligned with the optical axis of the left eye 60 and,thus, substantially parallel to the optical axis 84. The image from theouter optical component 88 is projected along an optical axis 96 that isoffset from the optical axis 94 by an angle ranging from 30 degrees to35 degrees, preferably approximately 30 degrees. As best shown in FIG.2, the two eyepiece optical systems 70 for each of the housings 54 and56 are positioned adjacent to each other so that both images at theoutput ends 80 and 92 appear continuous without a noticeable line ofdemarcation between the exit elements of the eyepiece optical systems.With respect to the forward looking direction, the two adjacent eyepieceoptical systems for each housing 54 and 56 provide a continuoushorizontal field of view that begins about 50 degrees to the right (orto the left) and ends 15 degrees to the left (or to the right).

As shown in FIG. 1, the optical systems are in line with the line ofsight of the observer's eyes 58 and 60. In addition, as shown in FIG. 2,the output ends 80 and 92 may each be offset below their respectiveinput ends 72 and 90. This is accomplished by inserting well knownmirror systems or prism systems (not shown) between the output ends 78of the image intensifier tubes 68 and the eyepiece optical components70. The apparatus also includes a well-known mechanism 98 for adjustingthe interpupillary distance between the eyepiece optical systems in thetwo housings 54 and 56 to accommodate different users.

The field of view 100 generated by the light simultaneously transmittedalong the four optical axes 82, 84, 94, 96 to the observer isschematically shown in FIG. 3. The field of view 100 is the result ofhaving the sub-fields of view formed from each of the output ends 80 and92 overlap one another. Each of the four sub-fields of view are circularhaving a horizontal field of view of approximately 40 degrees and avertical field of view of approximately 40 degrees. The field of view100 includes two peripheral portions 102 and 104 that are separated fromone another and each portion 102 and 104 has a monocular effect on theobserver. The field of view 100 includes an overlapping central portion106 spanning approximately 30 degrees. The central portion 106 ispositioned between the monocular portions 102 and 104 and is viewed byboth eyes 58 and 60 of the observer so as to provide full depthperception and exact stereo vision in the central portion. The field ofview 100 has a vertical field of view of approximately 40 degrees and ahorizontal field of view of approximately 100 degrees.

The above described binocular-like vision system 50 of FIGS. 1–3 has amass of approximately 550 g, a micro-channel plate (MCP) pitch ofranging from 6 to 7 microns, a limiting resolution of greater than orequal to 60 LP/mm, eye relief of greater than or equal to 20 mm andsystem resolution of approximately 1.15 cy/mr min. Note that in order toproduce a distortion-free system 50, the magnifications of all fouroptical components 62, 64, 86 and 88 must be controlled to be within2.5% of each other. In addition, a coupled focus mechanism 108 isprovided to adjust the position of the input ends in the X and Ydirections so that any mismatch between two adjacent images at theoutput ends is eliminated.

Other variations of the binocular-like vision system 50 are possible byvarying the objective and eyepiece optical systems 66 and 70 in numerousways in a manner well known in the art. For example, a horizontal fieldof view of—approximately 120 degrees and a vertical field of view ofapproximately 50 degrees is formed by the binocular-like vision system50 of FIGS. 4–6. The binocular-like vision system 50 of FIGS. 4–6basically has the same structure as and functions like the system 50previously described with respect to FIGS. 1–3 with some minor changesto the objective optical components 66 and the eyepiece opticalcomponents 70 of the optical components 62, 64, 86 and 88. The imageintensifier tubes 68 are unchanged.

As with the vision system 50 of FIGS. 1–3, the inner optical components62, 86 and the outer optical components 64 and 88 each have identicaloptical structures. The objective optical system 66 and eyepiece opticalsystem 70 can be of conventional design, such as disclosed in U.S. Pat.No. 5,416,315, the entire contents of which are incorporated herein byreference. The objective optical system 66 includes approximately 2 to 7optical elements, such as plastic or glass lenses L, which have aneffective focal length of approximately 17-mm. The eyepiece opticalsystem 70 includes approximately 2 to 7 optical elements, such asplastic or glass lenses L, which have an effective focal length ofapproximately 22 mm. The lenses L of both the objective optical systems66 and the eyepiece optical systems 70 are preferably spherical oraspherical in design.

As shown in FIG. 4, the optical axes 84 and 94 are aligned with theoptical axes of the right and left eyes 58 and 60, respectively, of theobserver. The optical axes 82 and 96 are offset from the optical axes 84and 94, respectively, by approximately 35 degrees.

The field of view 100 generated by the light simultaneously transmittedalong the four optical axes 82, 84, 94 and 96 is schematically shown inFIG. 6. The field of view 100 is the result of having the sub-fields ofview formed from the output ends 80 and 92 overlapping one another. Thefour sub-fields of view each are circular having a horizontal field ofview of approximately 50 degrees and a vertical field of view ofapproximately 50 degrees. In a manner similar to that shown in FIG. 3,the field of view 100 includes two monocular portions 102, 104 and a35-degree binocular portion 106. The field of view 100 has a verticalfield of view of approximately 50 degrees and a horizontal field of viewof approximately 120 degrees.

The above described binocular-like vision system 50 of FIGS. 4–6 has amass of approximately 550 g, a limiting resolution ranging from 57 to 60LP/mm and a system resolution of approximately 0.93 cy/mr mm.

The binocular-like vision system 50 of FIGS. 7–9 basically has the samestructure as and functions like the vision system 50 previouslydescribed with respect to FIGS. 4-6 where the objective opticalcomponents 66 of the inner and outer optical components 62, 64, 86 and88 are each replaced with an identical 26 to 27 mm effective focallength objective optical component 66 sold by Night Vision Corporationunder the NOVA-8 trademark. The image intensifier tubes 68 are also soldby Night Vision Corporation under the NOVA-8 trademark.

As with the vision system 50 of FIGS. 1–6, the inner optical components62, 86 and the outer optical components 64 and 88 each have identicaloptical structures for the objective optical systems 66, the imageintensifier tubes 68 and the eyepiece optical systems 70. The eyepieceoptical system 70 can be of conventional design, such as disclosed inU.S. Pat. No. 5,416,315, the entire contents of which are incorporatedherein by reference. The eyepiece optical system 70 includesapproximately 2 to 7 optical elements, such as plastic or glass lensesL, which have an effective focal length of approximately 26 to 27 mm.The lenses L of both the objective optical system 66 and the eyepieceoptical system 70 are preferably spherical or aspherical in design.

As shown in FIG. 7, the optical axes 84 and 94 are aligned with theoptical axes of the right and left eyes 58 and 60, respectively, of theobserver. The optical axes 82 and 96 are offset from the optical axes 84and 94, respectively, by approximately 35 degrees.

The field of view 100 generated by the light simultaneously transmittedalong the four optical axes 82, 84, 94 and 96 is schematically shown inFIG. 9. The field of view 100 is the result of having the sub-fields ofview formed from the output ends 80 and 92 overlapping one another. Thefour sub-fields of view each are circular having a horizontal field ofview of approximately 50 degrees and a vertical field of view ofapproximately 50 degrees. In a manner similar to that shown in FIG. 3,the field of view 100 includes two monocular portions 102, 104 and a35-degree binocular portion 106. The field of view 100 has a verticalfield of view of approximately 50 degrees and a horizontal field of viewof approximately 120 degrees.

The above described binocular-like vision system 50 of FIGS. 7–9 has amass of approximately 950 g, a limiting resolution of greater than 60LP/mm, a MCP pitch of 6–7 microns and a system resolution ranging from1.1 to 1.4 cy/mr min.

A fourth embodiment of a binocular-like vision system according to thepresent invention is shown in FIGS. 10–15. More particularly, FIGS.10–15 illustrate a vision visor system in which a binocular-like visionsystem 50 is mounted to a helmet-mounted visor 110 for use by aircraftpilots and the like. As shown in FIGS. 14–15, the visor 110 is mountedto the helmet 112 by an Aviator Night Vision Imaging System (ANVIS)-typemount 114. The mount 114 allows the visor 110 to move between a downposition in front of the eyes of the observer during use and an upposition away from the observer's face when not in use. The visionsystem 50 typically includes input ports to project Head-up display(HUD) information and for other purposes, suitable power sourcecouplings and other structures that do not form a part of the presentinvention and are thus not described herein.

The binocular-like vision system 50 of FIGS. 10–15 generally has thesame structure as and functions like the vision system 50 previouslydescribed with respect to the systems 50 of FIGS. 1–9 where theobjective and eyepiece optical components 66 and 70 of the inner andouter optical components 62, 64, 86 and 88 are each replaced withoptical components to give a desired field of view. As with the visionsystem 50 of FIGS. 1–9, the inner optical components 62, 86 and theouter optical components 64 and 88 each have identical opticalstructures for the objective optical systems 66, the image intensifiertubes 68 and the eyepiece optical systems 70. The objective and eyepieceoptical systems 66 and 70 can be of conventional design, such asdisclosed in U.S. Pat. No. 5,416,315, the entire contents of which areincorporated herein by reference. The objective optical system 66includes approximately optical elements, such as plastic or glass lensesL, which have an effective focal length of approximately 21.9-mm. Theeyepiece optical system 70 includes approximately optical elements, suchas plastic or glass lenses L, which have an effective focal length ofapproximately 21.9-mm. The lenses L of both the objective optical system66 and the eyepiece optical system 70 are preferably spherical oraspherical in design.

As shown in FIGS. 10–11 and 14 15, all four light components 62, 64, 86and 88 have light paths which are folded in contrast to the linear likelight paths of the binocular-like vision systems 50 of FIGS. 1–9. Thefolded light paths are formed by a number of well known fold prismsalong the optical paths and between the image intensifier tubes 68 andthe eyepiece optical systems 70 in a manner as described in U.S. Pat.No. 5,416,315, the entire contents of which are incorporated herein byreference. The folded optical paths allow the apparatus to be packagedradially close to the face along the contour of the visor 110, therebyminimizing any resulting shift in the center of gravity of totalhead-borne weight. The apparatus also provides a low profile thatminimizes any adverse aerodynamic effects that might develop underwindblast conditioning.

As shown in FIG. 11, the optical axes 84 and 94 are aligned with theoptical axes of the right and left eyes 58 and 60, respectively, of theobserver. The optical axes 82 and 96 are offset from the optical axes 84and 94, respectively, by approximately 35 degrees.

The field of view 100 generated by the light simultaneously transmittedalong the four optical axes 82, 84, 94 and 96 is schematically shown inFIG. 12. The field of view 100 is the result of having the sub-fields ofview formed from the output ends 80 and 92 overlapping one another. Thefour sub-fields of view each are circular having a horizontal field ofview of approximately 40 degrees and a vertical field of view ofapproximately 40 degrees. In a manner similar to that shown in FIG. 3,the field of view 100 includes two monocular portions 102, 104 and a35-degree binocular portion 106. The field of view 100 has a verticalfield of view of approximately 40 degrees and a horizontal field of viewof approximately 100 degrees.

The above described binocular-like vision system 50 of FIGS. 10–15 has amass of approximately 550 g, a limiting resolution of approximately 60LP/mm, an eye relief of 20 mm min., a system gain of 3,000 min., and asystem resolution of approximately 1.10 cy/mr min.

Note that each of the objective optical systems 62, 64, 86, 88 ismounted in and extends slightly through an opening provided in the visor110 and is mounted to the visor 110 by suitable bearings or the like.Although the objective optical systems 66 are fixed in position in thevisor 110, the eyepiece optical systems 70 are adjustable by adjustmentknobs 116 (FIG. 10) to match the interpupillary distances of the users.The housings carrying the objective optical systems 66 are rotatable intheir respective bearings to permit the eyepiece optical systems 70 tobe adjusted in position. Various structural details and advantageousfeatures of the visor-mounted panoramic night vision apparatus 50 ofFIGS. 10–15 are described in detail in U.S. Pat. No. 5,416,315, thedisclosure of such patent is hereby incorporated herein by reference.

The binocular-like vision system 50 of FIGS. 10–15 may also include ahead-up display (HUD) unit 114 for the display of secondary informationsuch as aircraft data and symbology to the pilot and crew. A combinerelement 120 is used to superimpose HUD information onto theimage-intensified scene of the right eye 58 so that they appear in thesame plane. Thus, no change of the eye's distance adaptation is needed.The HUD information defines a rectangular region 122 of approximately 28degrees wide by 20 degrees high in the field of view 100 centered on theuser's forward-looking line of sight as shown in FIG. 13.

The HUD information is preferably provided in a contrasting color (e.g.,yellow) to the green image intensified scene, and because the HUD andthe image intensifier tube provide information in different colors, adichroic combiner is used. As a result, the system will provide highbrightness for both images without requiring excessive luminance fromeither of the two sources.

The head-up display 114 in FIGS. 10–11 and 14–15 is preferably anelectroluminescent display although it may also comprise a liquidcrystal display (LCD). In this regard, reference is made to U.S. Pat.No. 5,254,852, the entire contents of which are incorporated herein byreference, which describes the use of a liquid crystal display devicefor presenting a secondary image to a user in a night imaging system.

In general, the information presented on the electronic display isselected and formatted in a computer and is presented to the displaysubsystem as a nominal RS-170 or the like monochrome, on-off (no grayscale or with gray scale type) signal. The display panel is capable ofproducing a minimum of 480-row by 640-column to 1024×1080 (SVGA) pixelimages. Since the combiner 120 is used, the HUD image is projectedcontinuously and the user perceives yellow symbols overlaying theintensified image.

Incorporation of the HUD unit 114 into the panoramic night visionimaging apparatus 50 adds very little weight to the overall apparatus(e.g., about 65 grams); and, accordingly, the overall apparatus remainsejection safe with a minimal shift in the center of gravity of the totalheadborne weight.

In the embodiments described with reference to FIGS. 1–15, panoramicnight vision imaging apparatus are described. As shown in FIGS. 17–23,the present invention may also be utilized in imaging apparatus that donot include image-intensifying means. The binocular-like vision systems50 of FIGS. 17–23 generally have the same structure as and function likethe system 50 previously described with respect to the systems 50 ofFIGS. 1–15. One difference between the vision system 50 of FIGS. 1–15and FIGS. 17–23 is that the light from the objective optical systems 66will be transferred directly to the eyepiece optical systems 70 withoutbeing intensified by an image intensifier tube in the systems of FIGS.17–23. Like the vision systems 50 of FIGS. 1–15, the vision systems ofFIGS. 17–23 are able to produce an enlarged field of view by using twooptical components per eye. The vision systems 50 of FIGS. 17–23 willproduce a field of view that is larger than the 43-degree field ofvision produced by the prior art binoculars of FIG. 16, which are a setof Jason 7×35 PermaFocus binoculars producing a horizontal field of viewof 113 yards at a distance of 1000 yards.

The binocular-like vision systems 50 of FIGS. 17–23 include inneroptical components 62, 86 and outer optical components 64 and 88, eachcomponent having identical optical structures for the objective opticalsystems 66 and the eyepiece optical systems 70. The objective andeyepiece optical systems 66 and 70 can be of conventional design, suchas disclosed in U.S. Pat. No. 5,416,315, the entire contents of whichare incorporated herein by reference. The objective optical system 66includes approximately 2 to 7 optical elements, such as plastic or glasslenses L, which have an effective focal length of approximately 160-mm.The eyepiece optical system 70 includes approximately 2 to 7 opticalelements, such as plastic or glass lenses L, which have an effectivefocal length of approximately 25-mm. The lenses L of both the objectiveoptical system 66 and the eyepiece optical system 70 are preferablyspherical or aspherical in design.

As shown in FIGS. 17 and 21, the light from the four objective opticalsystems 66 is transmitted to intermediate optical components 124 and 126before entering the eyepiece optical systems 70. Optical component 124preferably is a Porro prism that rotates the image from the inneroptical components 62 and 86 by 180 degrees so as to present an uprightimage to the observer. Optical component 126 preferably is a Schmidtprism that rotates and bends the image from the outer optical components64 and 88 so as to present an upright image.

As shown in FIGS. 17 and 21, the optical axes 84 and 94 are aligned withthe optical axes of the right and left eyes 58 and 60, respectively, ofthe observer. The optical axes 82 and 96 are offset from the opticalaxes 84 and 94, respectively, by approximately 35 degrees.

The field of view 100 generated by the light transmitted along the fouroptical axes 82, 84, 94 and 96 shown in FIGS. 17 and 21 is similar tothat shown in FIG. 6. The field of view 100 is the result of having thesub-fields of view formed from the output ends 80 and 92 overlapping oneanother. The four sub-fields of view each are circular having ahorizontal field of view of approximately 50 degrees and a verticalfield of view of approximately 50 degrees. The field of view 100includes two monocular portions 102, 104 and a 35-degree binocularportion 106. The field of view 100 has a vertical field of view ofapproximately 50 degrees and a horizontal field of view of approximately120 degrees. The binocular-like vision system 50 of FIG. 17, forexample, theoretically produces a horizontal field of view of 495 yardsat a distance of 1000 yards. The vision system 50 of FIGS. 18–23produces a horizontal field of view of 1058 feet at 1000 yards.

As in previous embodiments of FIGS. 1–15, the eyepiece optical systems70 in each housing 54 and 56 are positioned adjacent to each other sothat the overall panoramic image appears continuous without a noticeableline of demarcation between the exit elements of the eyepiece.

The vision system 50 of FIGS. 18–23 differs from the vision system 50 ofFIG. 17 in several ways. First, the outer components 64 and 88 of thevision system 50 of FIGS. 18–23 each include a wedge-shaped lens 128inserted at the input end 72. The lens 128 deflects the line of visionentering the outer components 64 and 88 in a well-known manner. Theouter components 64 and 88 further include a mirror 130 that directslight from the objective optical system 66 to a pair of wedged-shapedlenses 132 and 134 that are located adjacent to the prism 126. As shownin FIG. 21, the lenses 132 and 134 are arranged on each other to formparallel input and output sides 136 and 138, respectively. The lenses132 and 134 correct the color generated by the lens 128.

An even further embodiment of the invention is shown in FIGS. 24–29intended particularly for use in connection with flights having no highG considerations, such as helicopter and transport flights. In such asetting where there is no ejection capability, there is less concern forreduced center of gravity. A vision system 150 is shown having an inputend (172, 190) that receives light from an object and an opticaltransfer system (162, 164, 186, 188) that receives the light receivedfrom the input end and transfers the received light to an output end(180, 192) of the system, wherein light transmitted out of the outputend forms a field of view of the object that is greater than a 60-degreehorizontal field of vision. Studies by the U.S. Army suggest that themost efficient field of view for night aviation is about 80 degrees. Itis a common problem in night vision, however, that increasing the fieldof vision adversely affects resolution. The system of this inventionenhances both factors.

FIG. 24 shows the further embodiment of a binocular-like vision system150 contained in a housing assembly 152 having a pair of housings 154and 156 connected to one another by a bridge 157. Housings 154 and 156are arranged for respectively covering the right eye 158 and the lefteye 160 of an observer.

Each of housings 154 and 156 contains identical optical systems whichare mirror images of each other about a plane 163 (denoted by dashedlines) that bisects the housing assembly 152 as shown in FIGS. 24 and25. Accordingly, the discussion to follow regarding the housing 154 isequally applicable to the housing 156.

As shown in FIG. 24, the housing 154 includes two separate opticalcomponents 162 and 164. The inner optical component 162 has theidentical optical structure as the inner optical component 186 ofhousing 156. Accordingly, the discussion to follow regarding thestructure of the inner optical component 162 is equally applicable tothe optical component 186. The inner optical component 162 includesthree main optical structures—(1) an objective optical system 166, (2)an image intensifier tube 168 and (3) an eyepiece optical system 170.The objective optical system 166 defines an input end 172 that receiveslight from an object and includes intensifier tube 168. The objectiveoptical system 166 defines input end 172 that receives light from anobject. The objective optical system 166 includes output light from theimage intensifier tube 168 that is emitted by a green phosphor producinga visible band of light which is known as “P-20” or “P-43” light,although it will be appreciated that other image intensifierconstructions could also be used.

The image intensifier tube 168 is defined by a new 16-mm format,high-resolution, tube that is lighter in weight than the conventional18-mm tube. Because four tubes are utilized in this system, as comparedto the two 18-mm tubes used in conventional design, it is critical thatthe 16-mm takes 168 be much lighter suitable tubes are available fromITT Night Vision Roanoke, Va. Tube 168 includes a fiber optic bundlewell-known in the art for transmitting bits of image data from aphotocathode input end to a phosphor output end thereof in the mannervery similar to that described above in relation with the embodimentsshown and described in relation to FIGS. 1–23. The fiber optic bundle ispreferably twisted in a manner well known in the art to provide an imagerotation of 180 degrees so that an upright image of the object will bepresented to the eye of the observer.

The intensified visible output image generated by the image intensifiertube 168 is transferred to an output end 180 of the inner opticalcomponent 162 via the eyepiece optical system 170. The light transmittedthrough the output end 180 is transmitted along the optical axis 184that is aligned with the optical axis of the right eye 158. The eyepieceoptical system 170 can be of conventional design, such as disclosed inU.S. Pat. No. 5,416,315, the entire contents of which are incorporatedherein by reference. The eyepiece optical system 170 includesapproximately 2 to 7 optical elements, such as plastic or glass lensesL, which have an effective focal length of approximately, 24 mm, P/1.2.The lenses L of the objective optical system are preferably spherical oraspherical in design.

In order to enlarge the field of view, outer optical component 164 isprovided to also direct light from the object to the observer. Outeroptical component 164 includes an image intensifier tube and 168 anoptical arrangement substantially similar to the folded objectiveoptical system 66 shown and described above in relation to FIGS. 10 and11 above, which can be of a design disclosed in U.S. Pat. No. 5,416,315.Outer optical component 164 includes approximately 2 to 7 opticalelements, such as plastic or glass lenses L, which have an effectivefocal length of approximately 24-mm. The lense L of optical component164 are preferably spherical or aspherical in design. The folded opticalpath of the outer components 164 and 188 allows their respective inputends to be spaced laterally closer to the input ends of inner components162 and 186 to reduce parallax.

The above-described outer optical component 164 operates in a mannersuch that the input end 172 of the outer optical component 164 receiveslight from an object. The received light is then transferred via theobjective optical system via a mirror 164 a and subsequently a prism 164b to the input end of the image intensifier 168 defined by a fieldflattenen lense 168 a. Image intensifies to be 168 generates anintensified image that is received by the eyepiece optical system 170.The eyepiece optical system 170 then sends the image to an output end180 of the outer optical component 164. The light transmitted throughthe output end 180 travels along an optical axis 182 that is offset fromthe optical axis 184 of inner optical component 162 by an angle rangingfrom approximately 30 degree to 35 degree and which is preferably about30 degrees. Electrical power is provided to both tubes 168 of components162 and 164 by electrical wiper contact 169.

As stated previously, the inner optical component 186 for the left eye160 has the same structure and operates in the same manner as the inneroptical component 162. Similarly, the outer optical component 188 forthe left eye 160 has the same structure and operates in the same manneras the outer optical component 164. In other words, the inner and outeroptical components 186 and 188 of housing 156 each receive light from anobject at the input ends 90 and transfer their images of the object torespective output ends 192. As shown in FIG. 24, the image from theinner optical component 186 passes through an intensifier tube which isthen projected along an optical axis 194 that is aligned with theoptical axis of the left eye 160 and, thus, substantially parallel tothe optical axis 184. The image from the outer optical component 188 isultimately projected along an optical axis 196 that is offset from theoptical axis 194 by an angle ranging from 30 degrees to 35 degrees,preferably approximately 30 degrees.

As shown in FIG. 25, the two eyepiece optical systems 170 for each ofthe housings 154 and 156 are positioned adjacent to each other so thatboth images at the output ends 180 and 192 appear continuous without anoticeable line of demarcation between the exit elements of the eyepieceoptical systems. With respect to the forward looking direction, the twoadjacent eyepiece optical systems for each housing 154 and 156 provide acontinuous horizontal field of view that begins about 50 degrees to theright (or to the left) and ends 15 degrees to the left (or to theright).

As shown in FIGS. 24 and 25, the optical systems are in line with theline of sight of the observer's eyes 158 and 160. The apparatus alsoincludes a well-known ANVIS mounting system 151 to, in a standardfashion, attach the night vision goggles of the present invention to thestandard-issue pilot's helmet. Mounting system 151 commonly includes amechanism 151 a for adjusting the interpupillary distance between theeyepiece optical systems in the two housings 54 and 56 to accommodatedifferent users. Mechanism 151 b is an adjustment dial for adjusting thefore/aft position of the system. The entire vision system 150 and bridge157 are detachably affixed to the pilot's helmet via mechanism 151 cthat is a well-known element of the ANVIS system.

The inner two objectives 166 and 186 of vision system 150 arefocus-adjustable 18 inches to infinity, and the outer optical components168 and 188 are fixed at infinity. The inner optical channels are notfolded and are designed with fast F/1.05 objective lenses. The outerchannels 168 and 188 employ a folded channel optics design with F/1.17objective lenses to reduce parallax and size. The effective focal lengthof the eyepiece is 24.0 mm, while the eye relief has been increased to30 mm. All of the mechanical adjustments currently used on the AN/AVS-6and AN/AVS-9 are the same (i.e., tilt, independent inter-pupillarydistance adjustment, up/down, fore/aft) and the like.

The field of view 200 generated by the light simultaneously transmittedalong the four optical axes 182, 184, 194, 196 to the observer isschematically shown in FIG. 26. The field of view 200 is the result ofhaving the sub-fields of view formed from each of the output ends 180and 192 overlap one another. As shown particularly in FIG. 26, each ofthe four sub-fields of view are circular having a horizontal field ofview of approximately 40 degrees and a vertical field of view ofapproximately 40 degrees. The field of view 200 includes two peripheralportions 202 and 204 that are separated from one another, wherein eachportion 202 and 204 has a monocular effect on the observer. The field ofview 200 includes an overlapping central portion 206 spanningapproximately 30 degrees. The central portion 206 is positioned betweenthe monocular portions 202 and 204 and is viewed by both eyes 158 and160 of the observer so as to provide full depth perception and exactstereo vision in the central portion. The field of view 200 has avertical field of view of approximately 40 degrees and a horizontalfield of view of approximately 100 degrees.

The binocular-like vision system 150 of FIGS. 27 and 28 may also includea head-up display (HUD) unit 214 for the display of secondaryinformation such as aircraft data and symbology to the pilot and crew. Abeam combiner element 220 is used to superimpose HUD information ontothe image-intensified scene of the right eye 158 so that they appear inthe same plane. Thus, no change of the eye's distance adaptation isneeded. Combiner 220 reflects 10% of the light while transmitting 90%.HUD 214 is coupled to the control system of the aircraft via cable 215.The date the aircraft controller is transmitted by way of flexiblemulti-conductor connector 215′ complying the HUD with the objective. TheHUD information defines a rectangular region 222 of approximately 28degrees wide by 20 degrees high in the field of view 200 centered on theuser's forward-looking line of sight as shown in FIG. 29.

As with the HUD system of the alternative embodiments described above,the HUD information is preferably provided in a contrasting color (e.g.,yellow) to the green image intensified scene, and because the HUD andthe image intensifier tube provide information in different colors, adichroic or part silver type combiner is used. As a result, the systemwill provide high brightness for both images without requiring excessiveluminance from either of the two sources.

The head-up display shown in FIGS. 27 and 28 is commonly referred to asAMELD (active matrix ectroluminescent display), although it may alsocomprise a liquid crystal display (LCD). In this regard, reference ismade to U.S. Pat. No. 5,254,852, the entire contents of which areincorporated herein by reference, which describes the use of a liquidcrystal display device for presenting a secondary image to a user in anight imaging system. In general, the information presented on theelectronic display is selected and formatted in a computer and ispresented to the display subsystem as a nominal RS-170 or the likemonochrome, on-off (no gray scale or with gray scale type) visor-mountedpanoramic night vision apparatus 50 of FIGS. 10–15 are described indetail in U.S. Pat. No. 5,416,315, the disclosure of such patent ishereby incorporated herein by reference.

The binocular-like vision system 150 of FIGS. 24 and 25 has a mass ofapproximately 600 g, a limiting resolution of approximately 64 LP/mm, aneye relief of 30 mm min., a system gain of 8,000 min., and a systemresolution of approximately 1.3 cy/mr min. The binocular-like visionsystem 150 of FIGS. 27 and 28 including the HUD element has a mass ofapproximately 650 g, a limiting resolution of approximately 64 LP/mm, aneye relief of 30 mm min., a system gain of 7,000 min., and a systemresolution of approximately 1.3 cy/mr min.

FIGS. 30–40 present yet another embodiment of the PNVG goggle, designedso that the individual optical channels are modular and thus detachablefrom each other. FIGS. 30 and 31 show the modular PNVG assembly 300 ofthis invention mounted on the visor 302 of an HGU-56/P helmet 304.Modular assembly 300 may be affixed to the visor 302 by conventionalmeans. Each of the 4 optical channels 310, 320, 330, 340 is a separatelysealed and self-contained module. Removal of any single module from thePNVG assembly 300 will not break any pressure seals or degrade theoptical performance of the removed module or any of the remainingmodules. Electrical power and information (i.e., data signals and thelike) required by a module is provided through electrical connectormeans provided between the modules. Such means could include, forexample, wiper contacts 312 provided on outer optical module 310 asshown in FIG. 37, and contact pads 328, 338 provided on inner opticalmodules 320, 330, respectively, as shown in FIG. 39.

The modules include attachment means that ensures proper positioning andalignment of the adjacently mating modules. As shown best in FIGS. 37and 39, such attachment means may include tongue-and-groove typeconnectors 314, 324, 334, by which each module is slidably received byand secured to an adjacent module. While in a preferred embodiment theintegral electrical connector contained within each module (such aswiper contacts 37 and relays 328 and 338) enables the electricalconnection between adjacent modules to be made simultaneously with themechanical attachment of the module, the electrical and data connectionsmay be made separately by way of, for example, cable connectors or thelike extending between adjacent modules.

In addition to the modularity of the four primary optical channels ofthe PNVG assembly 300, a display 360 (i.e., HUD) and a camera 370 aremodular as well. Similar to the individual optical modules, each ofthese components 360, 370 are separately sealed and self-containedmodules as well. Camera 370 may be of a type used conventionally withhelmet assemblies for flight operations. Removal of the display 360 orcamera 370 will not break any pressure seals or degrade the performanceof the removed module or of any of the remaining modules. Again,electrical power and information (i.e., data signals and the like)required by the camera or display is provided by electrical connectormeans provided on each module.

The field of view 400 generated by the light simultaneously transmittedalong the four optical axes of the modular components 310, 320, 330, 340is schematically shown in FIG. 38. The field of view 400 is the resultof having the sub-fields of view formed from the output ends of themodules overlapping one another. The field of view 400 includes twomonocular portions 402, 404, and a 40-degree binocular portion 406. Thefield of view 400 has a vertical field of view of approximately 40degrees and a total horizontal field of view of approximately 95degrees.

The outer optical modules are identical and interchangeable. Such amodule may be simply turned or flipped 180° to serve as the right outeror left outer module. The right inner and left inner modules arededicated and are not interchangeable.

A significant advantage provided by the modularity of this invention isthat one can employ if desired merely the dual-channel embodiment ofthis assembly as shown in FIGS. 33 and 34, comprising only the inneroptical modules 320, 330 and the bridge 350. Such an embodiment may alsoinclude the display 360 and camera 370 if desired. This allows an enduser to purchase only the dual-channel version as its budget permitsand, as needed or as finances permit, to purchase separately oneadditional component, the universal outer optical module, to convert thedual-channel system to panoramic. This is particularly beneficial fordeveloping countries with limited military budgets. This also allows thedual-channel assembly to be used by persons needing no or low lightcondition visibility but who do not need panoramic capability, such asthe aircraft or ground crew other than the pilot(s).

From an operations standpoint, each optical module operates in a mannersimilar to that of the non-modular optical channels discussed in theprevious embodiments. Thus, each optical module is designed to receivelight from an object being viewed at an input end 311, 321, 331, 341,and to transfer an image of the object to the input end of an internalimage intensifier means (not shown). The image intensifier means makesit possible for the observer to view an object in dark conditions byreceiving the visible and/or infrared light image of the objecttransferred to the input end thereof. The image intensifier meansconverts the received image to an intensified visible output image in apredetermined narrow band of wavelengths at its output end. For example,the image intensifier means may include a GaAs photocathode at its inputend. An optical transfer system that receives the light received fromthe input end then transfers the received light to an output end 313,323, 333, 343 of each module.

A further preferred embodiment of a night vision goggle system of thisinvention utilizes a spectral beamsplitter to enhance the low-lightlevel sensitivity and resolution of the system, to enable the nightmissions to be recorded for later analyses, to transmit the video imagesof the night scene to a remote location in real time, and to insert oroverlay the intensified image with images from other sensors and/or data

Referring now to FIG. 41, such an embodiment comprises a system 500shown schematically including a dichroic type narrow-band-pass filter502 used as a beamsplitter located inside the NVG eyepiece. This filter502 is combined with appropriately aligned polarizers 504, 506 androtators 508, 510 to direct the intensified images of the night scenefor recording, transmitting or further video processing. A miniaturevideo camera 512 captures the intensified scene, which in normal lightlevels allows the video to be recorded or transmitted to other remotelocations.

In this “direct view” mode, as shown in FIG. 41, polarizers 504, 506 androtators 508, 510 are aligned in a “P” orientation. The light from theimage intensifier passes through the shutter 510 (the L.C.-type shutterrotates rectangle area about 30°×22.5° size) but only the central bandof the P43 phosphor (538 to 553 nm) passes through the beamsplitter 502and through the second polarizer 504 to tile user's eye 514. Since allNVG eyepieces use only the central (green) band of the P43 phosphor, thesidebands must be filtered out (because of chromatic aberrations) andnot be allowed to reach the user's eye. These sidebands contain up to74% of the light energy relative to the central band and are normally“wasted” in present night vision goggle filter systems. The dichroictype beamsplitter 502 reflects all these side bands to the miniature CCDcamera 512 for recording or transmitting the real-time images to otherlocations.

FIG. 42 graphically depicts how the beamsplitter 502 reflects completelythose side bands of the image intensifier P43 phosphor that should notbe transmitted by the eyepiece.

The rotator 508 in the camera channel is aligned with the shutterpolarizer 510 as well as the display channel polarizer 506, thusproviding the capability to record and transmit the overlaid symbologyor any image projected by the display channel 516. These recorded andtransmitted images are identical to the images as seen by the user.

In the enhanced low light level (ELLL) mode, as schematically shown inFIG. 43, the shutter rotator and camera rotator 508 are energized androtated to an “S” orientation, thus preventing the light from the imageintensifier from being seen directly by the user. Similarly, the displayimage is blocked by the polarizer 508 of the camera 512 from enteringthe camera system in order to prevent undesirable feedback. In this ELLLmode, the intensified image is received by the camera 512. The camera'svideo image signal output is then amplified and electronically enhancedby a computer system on board the aircraft to reduce any noise producedby the image intensifier low light level scintillation. The enhanced andamplified video is then combined electronically with any symbology orother sensor's video signal and displayed through the display system 516to the user. This enhanced and combined video can be recorded exactly asseen by the user or transmitted to other remote locations.

Most image intensifiers produce a 40° circular field of view (FOV),while recording camera systems typically have a rectangular 30°horizontal by 22.5° vertical FOVs. The rectangular shape LC-type shutter510 is placed in close proximity to the image intensifier's output imagein order to block the eye from seeing the exact area that is beingviewed by the camera optical system. Similarly, the display system willhave the same FOV projected as the camera, thus producing the same sizeimage as the intensifier. In this ELLL mode, the user will see a 40°circular intensified image with an inserted rectangular 30° by 22.5°enhanced image and any symbology, similar to the “picture-in-picture”technology common in many of today's higher-priced television sets.

Although the system and method provided by the present invention havebeen described with a preferred embodiment, those skilled in the artwill understand that modifications and variations may be made withoutdeparting from the scope of this invention as set forth in the followingclaims. Such modifications and variations are considered to be withinthe purview and scope of the appended claims. For example, althoughvisor-mounted or helmet-mounted night vision imaging apparatus aredescribed herein, the apparatus could readily be designed for mountingdirectly to a helmet, if desired. In addition, the optical components ofFIGS. 1–43 may differ from each other as long as their effectivecomponents are able to achieve the desired parameters of the visionsystem, such as the desired magnification and effective focal lengths ofthe components of the system.

1. An image enhancement system for a night vision goggle system of thetype having an image intensifier for converting incoming infrared and/orvisible light to an intensified visible image for presentation via aneyepiece to the eyes of a user, said image enhancement systemcomprising: a pair of rotators; a pair of polarizers; and, a filter,said filter is positioned in alignment with said rotators and saidpolarizers; wherein central band light from the image intensifier isdirected to the eye of the user when said polarizers and rotators arealigned in a first orientation, and wherein said central band light isdirected away from the eye of the user when said polarizers and rotatorsare aligned in a second orientation.
 2. The system of claim 1 whereinsaid filter is a dichroic type narrow-band-pass filter.
 3. The system ofclaim 2 wherein said filter is contained in the eyepiece of the nightvision goggle.
 4. The system of claim 1 further comprising a camerachannel including a camera, wherein when said polarizers and rotatorsare aligned in said first orientation, said side band light from theimage intensifier is reflected to said camera, wherein real-time imagescan be recorded and transmitted, and when said polarizers and rotatorsare aligned in said second orientation, said central band light isdirected to said camera.
 5. The system of claim 4 wherein theintensified visible image presented to the user comprises a circularimage with a rectangular insert when said polarizers and rotators arealigned in said second orientation.
 6. The system of claim 4 whereinsaid pair of rotators are liquid crystal type shutters.
 7. The system ofclaim 1 further comprising a display channel including a display fordisplaying secondary information to the user and to the camera when saidpolarizers and rotators are aligned in said first orientation.
 8. Thesystem of claim 1 wherein the intensified visible image presented to theuser comprises a circular image with a rectangular insert when saidpolarizers and rotators are aligned in said second orientation.
 9. Thesystem of claim 1 wherein said filter is contained in the eyepiece ofthe night vision goggle.
 10. The system of claim 1 wherein said pair ofrotators are liquid crystal type shutters.
 11. A method for enhancing animage of a night scene produced by the image intensifier of a nightvision goggle system, which comprises: passing light from the imageintensifier through a first polarizer to produce polarized light;filtering said polarized light through a filter, wherein said polarizedlight is split into at least central band light and side band light;directing said central band light through a second polarizer to the eyeof a user; and providing a camera channel including a third polarizerand a camera, directing said side band light through said thirdpolarizer and to said camera for recording or transmitting real-limeimages.
 12. The method of claim 11 wherein at least said first polarizeris a liquid crystal type shutter.
 13. The method of claim 11 whereinsaid filter is a dichroic type narrow-band-pass filter.
 14. The methodof claim 13 wherein at least said first polarizer is a liquid crystaltype shutter.
 15. The method of claim 11 wherein said first polarizerand said third polarizer are liquid crystal type shutters.
 16. Themethod of claim 11 further comprising providing a display channelincluding a fourth polarizer and a display, orienting said fourthpolarizer relative to said filter such that said central band light isdirected to the eye of said user.
 17. The method of claim 16 whereinsaid filter is a dichroic type narrow-band-pass filter.
 18. The methodof claim 17 including the step of electronically enhancing said videoimage signal output to produce enhanced video image signal output. 19.The method of claim 18 including the step of combining secondaryinformation with said enhanced video image signal output.
 20. The methodof claim 19 including further the step of directing said combined andenhanced video via said display to the eye of the user.
 21. The methodof claim 20 including the step of recording said combined and enhancedvideo.
 22. The method of claim 21 including the step of transmittingsaid combined and enhanced video.
 23. The system of claim 22 whereinsaid filter is located inside the eyepiece of the night vision goggle.24. The method of claim 23 wherein said first polarizer and said thirdpolarizer are liquid crystal type shutters.
 25. The method of claim 11wherein said filter is a dichroic type narrow-band-pass filter.
 26. Themethod of claim 25 wherein said first polarizer and said third polarizerare liquid crystal type shutters.
 27. An image enhancement system for anight vision goggle system of the type having an image intensifier forconverting incoming infrared and/or visible light to an intensifiedvisible image for presentation via an eyepiece to the eyes of a user,said image enhancement system comprising: beamsplitting means forsplitting light from the image intensifier into a central band and sidebands; and directing means in alignment with said beamsplitting meansfor directing said central band and said side bands, wherein saiddirecting means is adjustable between a first position and a secondposition.
 28. The system of claim 27 including a camera channel thatincludes a camera, and a display channel that includes a display system,wherein said directing means directs said central band through saideyepiece to the eyes of the user and directs said side bands throughsaid camera channel to said camera when said directing means is in saidfirst position, and said directing means directs said central band lightthrough said camera channel to said camera when said directing means isin said second position.
 29. The system of claim 27 wherein saiddirecting means comprises a pair of rotators and a pair of polarizers.30. The system of claim 29 wherein said rotators are liquid crystal typeshutters.
 31. The system of claim 27 wherein said beamsplitting means isa dichroic type narrow-band-pass filter.